I was checking a permaculture site for new posts, and came across a post on seasoning. AND she uses a metal spatula, too!

She says that bacon fat, lard or palm shortening are best, much better than vegetable oil. Also, she says that "heating the fat for the polymerizing action makes a big difference."

(It's the last entry of the thread)
Permaculture forums

Sue

Mmm, bacon. Though I'm worried about the polymerizing action in my arteries. :-)

I have a cast iron pan that was my granny's, and I'd love to get it back into action.

I'm also told that cooking with cast iron helps the DW by upping the iron content in food.

I would tend to agree, except that bacon fat has salt in it, which can cause some problems if it is used to season younger pots and pans that don't already have a good seasoning coat built up. Palm shortening is excellent, and is one of the ingredients in Camp Chef's Cast Iron conditioner for much the same reason. Actually, I believe that heating the oil/grease to the scorch point, which is necessary to get a good seasoning coat, is a depolymerization process, as the heat is breaking down the material and "volatizing" off the lighter compounds, progessively leaving behind a residue that eventually becomes a carbonized solid. Blast may have better insight into the chemical decomposition process than I do. As far as the metal utensils go, I guess you can either scrub or scrape, whichever works best for you. I can and have used metal utensils in my cast iron, but I do not recommend it, nor should it be necessary. To each his own. If it works, then by all means, indulge.

Unless you let your pots get rusty, you will not increase the iron uptake from eating out of well seasoned cast iron. I try to keep my pots and pans seasoned so that an unpermissive barrier is maintained between the food and the metal surface.